Signal transformers

This function corresponds to the iterate function for lists.
Begins with an initial output value. Each time an input function is
received, it is applied to the current accumulator and the new value
is emitted.

One-instant delay. Delay the signal for an instant returning the
argument value at the first instant. This wire is mainly useful to
add feedback support to wires, which wouldn't support it by
themselves. For example, the FRP.NetWire.Analyze.avg wire does not
support feedback by itself, but the following works: